A systematic analysis of the structure, function and regulation of the pyruvate, Alpha-ketoglutarate, and branched chain Alpha-keto acid dehydrogenase multienzyme complexes will be continued. The specific aims are (1) to purify the branched chain Alpha-keto acid dehydrogenase phosphatase from bovine kidney to homogeneity, determine its subunit composition, and further characterize its regulation; (2) to purify and characterize the branched chain Alpha-keto acid dehydrogenase kinase from bovine kidney; (3) to further characterize pyruvate dehydrogenase phosphatase and pyruvate dehydrogenase kinase from bovine kidney and heart; (4) to separate the two different subunits comprising the pyruvate dehydrogenase component of the mammalian pyruvate dehydrogenase complex and determine the function of each subunit; (5) to continue structural studies on the Alpha-keto acid dehydrogenase complexes, subcomplexes and component enzymes thereof, using limited proteolysis, electron microscopy and X-ray diffraction. The mitochondrial pyruvate and branched chain Alpha-keto acid dehydrogenase complexes occupy key positions in metabolism, and their activities are under metabolic and hormonal control. Regulation of the flux of carbon through the pyruvate dehydrogenase complex plays an essential role in the control of energy metabolism. The branched chain Alpha-keto acids derived from the branched chain amino acids, valine, leucine and isoleucine, represent an important source of carbon for cellular energy generation, carbohydrate biosynthesis and ketone body production in various tissues. Elucidation of the structure and catalytic and regulatory properties of the isolated Alpha-keto acid dehydrogenase complexes and their component enzymes is a necessary prerequisite to understanding the in vivo regulation of their activities. Also, analysis of inherited and acquired disorders of pyruvate and branched chain amino acid metabolism that have been reported rests on knowledge of normal metabolism of these substances.